The answer is that it is mainly about Hitchcock’s films, though Truffaut is instrumental in allowing you to appreciate them.

In 1962 Truffaut interviewed Hitchcock over a period of about a week, the transcripts being later published in a book (entitled simply Hitchcock) alongside stills from his films. They spoke about the craft of film, the nuts and bolts of directing – rather like The Paris Review’s writers’ interviews, come to think of it – and that is what made it such a valuable document for aspiring filmmakers like Martin Scorsese and Paul Schrader, two of several directors interviewed in the film.

Two observations struck home. One, Hitchcock began in the silent era and most of his films would work perfectly well (or so it was claimed) without dialogue. Whether one could dispense with the music – Bernard Herrmann’s scores, say- is another matter entirely. Two, Hitchcock’s whole approach required that the actor be part of an overall, predetermined vision. The actor could never dominate and the films would work perfectly well with mediocre actors (The Birds being a case in point). The upshot is that when Hitchcock worked with a really great actor (James Stewart or Henry Fonda or Montgomery Clift) he never got the best out of them – that just wasn’t his forte or his focus of interest. I’m unsure about the absolute validity of this, but there’s certainly something to it. Did any actor in a Hitchcock film ever receive an Oscar?

This is an essential watch for anyone with an interest in Hitchcock and the art and craft of film.